The findings could help design more effective head protection for humans.

For years, scientists have examined the anatomy of woodpeckers' skulls to find out how they pull off their powerful pecking without causing themselves harm.

The birds have little "sub-dural space" between their brains and their skulls, so the brain does not have room to bump around as it does in humans. Also, their brains are longer top-to-bottom than front-to-back, meaning the force against the skull is spread over a larger brain area.

A highly-developed bone called the hyoid - which in humans is just above the "Adam's apple" - has also been studied: starting at the underside of the birds' beaks, it makes a full loop through their nostrils, under and around the back of their skulls, over the top and meeting again before the forehead.